A known valve timing control device includes a driving side rotational member synchronously rotatable with a crankshaft of an internal combustion engine, a driven side rotational member arranged coaxially with the driving side rotational member and synchronously rotatable with a camshaft that controls an opening and closing operation of valves of the internal combustion engine, a retarded angle chamber defmed by the driving side rotational member and the driven side rotational member and displacing a relative rotational phase of the driven side rotational member to the driving side rotational member in a retarded angle direction by a supply of a fluid to the retarded angle chamber, an advanced angle chamber defmed by the driving side rotational member and the driven side rotational member and displacing the relative rotational phase in an advanced angle direction by the supply of the fluid to the advanced angle chamber, a fluid supply and discharge mechanism for supplying the fluid to the advanced angle chamber and the retarded angle chamber and for discharging the fluid from the advanced angle chamber and the retarded angle chamber, and a lock mechanism for locking the relative rotational phase at a predetermined lock phase.
The aforementioned valve timing control device, which is used in an internal combustion engine such as an automobile engine, controls the opening and closing timing of the valves by displacing the relative rotational phase of the driven side rotational phase to the driving side rotational phase so that the internal combustion engine can be appropriately operated. In addition, the valve timing control device locks the relative rotational phase at the predetermined lock phase in which an appropriate opening and closing timing of the valves can be obtained when starting the internal combustion engine.
Such valve timing control device is disclosed in JP2004-116412A. The valve timing control device disclosed includes a lock mechanism constituted by a recess portion formed at a driven side rotational member and two lock members formed at a driving side rotational member. The two lock members are inserted into the recess portion for achieving a locked state or retracted from the recess portion for achieving an unlocked state, and are constantly biased in a direction so that the lock members are inserted into the recess portion. According to the valve timing control device disclosed, when the two lock members are inserted into the recess portion so as to achieve the locked state, one of the lock members prevents displacement of the relative rotational phase of the driven side rotational member to the driving side rotational member in the retarded angle direction while the other one of the lock members prevents displacement of the relative rotational phase in the advanced angle direction. Then, by a supply of a portion of a fluid provided to the retarded angle chamber to the recess portion, the two lock members are retracted therefrom so as to achieve the unlocked state.
When or immediately after the internal combustion engine starts operating, the relative rotational phase should be locked at a phase different from the predetermined lock phase. However, according to the aforementioned valve timing control device, the relative rotation can be only locked at the single predetermined lock phase and may not be locked at the different phase. Immediately after the internal combustion engine starts operating, for example, the relative rotation should be locked at the phase different from the predetermined lock phase so as to reduce occurrence of hydrocarbon (i.e. cold HC). In addition, at the operation start of the internal combustion engine, an optimum opening and closing timing of the valve is not constant and may vary depending on a state of the internal mechanism such as a temperature of a combustion chamber. Accordingly, in order to obtain the optimum opening and closing timing of the valves when starting of the internal combustion engine, the relative rotation should be locked at the phase different from the predetermined lock phase.
Thus, a need exists for a valve timing control device that can lock a relative rotational phase between a driving side rotational member and a driven side rotational member at a phase different from a predetermined lock phase when or immediately after an internal combustion engine starts operating.